There is a requirement for screening of cargo for the purpose of identifying the presence of illicit materials and objects. Currently, such screening is often performed using X-ray scanners.
X-ray scanners for cargo inspection typically comprise a high energy X-ray source (usually based on an X-ray linear accelerator) with a beam quality of 4 MeV to 9 MeV. The X-ray output from the X-ray linear accelerator is then collimated down to a narrow fan-beam of radiation which is shone through the item of cargo under inspection. A linear array of X-ray detector elements is then positioned opposite to the X-ray source such that it is irradiated by the fan-beam of radiation after attenuation of the X-ray beam by the object under inspection.